Controlling the Product Selectivity of Oxygenate Transformations on Metal-Based Catalysts

The design of heterogeneous catalysts for selective chemical conversions is a critical factor in developing a more sustainable and efficient chemical industry. In particular, there is significant interest in developing catalysts for the production and valorization of C₂‒C₄ oxygenates, which are versatile platform chemicals, especially from alternative sources of carbon. Promising catalysts for such transformations have been identified, but fundamental understanding of the reaction mechanisms and active sites on these catalytic materials is still lacking. This work utilized three representative reactions to develop this fundamental understanding through the use of model surfaces, probe molecules, in-situ characterization, and reactor evaluation. The three classes of reactions that were investigated are alcohol dehydration and dehydrogenation, ethylene hydroformylation, and olefin epoxidation. This work elucidates how interactions between active species, surface intermediates, and catalyst/support interfaces influence the catalytic performance of catalysts based on bimetallic and transition metal nitride materials. The first part of this dissertation used ethanol and isopropanol as biomass model compounds to probe the active sites of metal-modified molybdenum nitride catalysts. The non-oxidative dehydrogenation of alcohols is a route to synthesize aldehydes from biomass-derived alcohols while simultaneously producing hydrogen. Comparing the reaction pathways of ethanol, the simplest molecule containing O−H, C−H, C−O and C−C bonds that are present in biomass-derived molecules, with isopropanol, the simplest secondary alcohol, provided useful insights into the upgrading of more complex biomass. Chapter 3 compared the two alcohols on Cu-modified molybdenum nitride, and Chapter 4 focused solely on the reaction of isopropanol over Fe- and Pt-modified molybdenum nitride. This work showed how the orientation of intermediates, chemical state of active centers, and metal d-band structures influenced the bond scission ...